A perennial problem in the mass spectrometric analysis of both biological and environmental samples is that the absolute level of analyte is extremely low. One approach to this problem is to develop low volume-high flux delivery systems for the mass spectrometer. We have undertaken the development of interfaces for nanoscale packed capillary LC and MS. These capillary systems offer the same advantages over wider-bore LC systems that capillary GC offers over packed-column GC, a high flux of analyte into the MS but with.a significantly lower total analyte level necessary. Current developments are in the areas of nanoscale capillary LC and capillary zone electrophoresis interfaced with both coaxial continuous flow fast atom bombardment MS and electrospray ionization MS. We have applied these techniques to separations of for example nucleosides, unusual modified nucleosides that have been found to be elevated in the urine of AIDS patients, macrolide antibiotics, and penicillins. We are currently investigation the separations of proteins by these methods.